Editing Bernal sphere (section)

===Island One===
[[File:Bernal sphere space habitat - O Neill Island One version.png|thumb|upright=3.8|Example layout for an Island One-type Bernal sphere]]
In a series of studies held at [[Stanford University]] in 1975 and 1976 with the purpose of speculating on designs for future [[space colonies]], Dr. [[Gerard K. O'Neill]] proposed ''Island One,'' a modified Bernal sphere with a diameter of only {{convert|500|m|ft|abbr=on}} rotating at 1.9 [[Revolutions per minute|RPM]]<!--faster was found to create difficulties with balance--> to produce a full [[Earth]] [[artificial gravity]] at the sphere's equator. The result would be an interior landscape that would resemble a large valley running all the way around the [[equator]] of the sphere. ''Island One'' would be capable of providing living and recreation space for a population of approximately 10,000 people, with a "Crystal Palace" habitat (consisting of several rings attached to the sphere at each pole) used for agriculture. Sunlight was to be provided to the interior of the sphere using external [[mirror]]s to direct it in through large windows near the poles. The form of a sphere was chosen for its optimum ability to contain air [[pressure]] and its optimum mass-efficiency at providing [[radiation shielding]].<ref name="ONeill" >{{cite book |last=O'Neill |first=Gerard K. |title=[[The High Frontier: Human Colonies in Space]] |edition=Third |publisher=[[Apogee Books]] |year=2000}}</ref>